More and more installations are coming into use which enable goods or services to be obtained by means of a smart card. A user may buy a smart card from an organization which provides goods or services and the organization loads the card's memory with data representative of money's worth. Such an installation includes both apparatus for processing smart cards, generally referred to as a "reader", and means for supplying the requested goods or services. A typical service is a telephone call. Two situations can then occur: either the card holder uses a service, e.g. makes a telephone call, with the processing apparatus deducting a corresponding amount from the card memory in small increments throughout the duration of the service, (with the service being stopped when the credit in the card runs out); or else the user indicates (either directly or indirectly) a lump sum corresponding to the goods or services required, for example the user may indicate a desire to purchase a particular object, and in this case the processing apparatus verifies that sufficient credit is available in the card, and if it is, it deduct the appropriate lump sum from the previous credit total in the card, and causes the requested goods or service to be supplied to the card holder.
Several different types of smart card are in existence. The simplest type, referred to as a "pre-paid" card, stores data in its memory identifying the goods or services for which the card may be used, together with a certain number of memory locations corresponding to a matching number of charge units which the card holder can spend using the card. As the card is used, the memory locations corresponding to the charge units are "burned" until all of the available charge units have been used up. A more sophisticated smart card has a memory storing data relating not only to the type of goods or services made available by the card, but also data relating to the identity of the card holder. The card still includes memory zones for storing the cumulated value of goods or services obtained using the card, and this cumulated total is compared with a predetermined maximum for which the card is good. Such a card may require its holder to key a code number into the installation offering goods or services prior to making such goods or services available.
Regardless of the type of goods or services concerned, and regardless of the degree of sophistication of the memory system implemented by the card, a card holder is always faced with the problem of determining, at least approximately, how much credit remains in the card for obtaining further goods or services.
Although processing apparatus frequently includes means for displaying data and in particular for displaying the credit remaining in a card, the card holder has no way of establishing this amount without actually inserting the card in appropriate apparatus. This makes it particularly difficult for a user to decide when to buy a new "pre-paid" card or when to have a card of the other type renewed. It is all too easy for a user to discover that a card is "used up" when attempting to obtain goods or services which are urgently needed and for which no other form of payment is immediately available, for example on a public holiday or at night.
There is also the problem of smart cards being used by blind people who simply cannot see the display indicating how much credit remains. It is unlikely that card processing apparatuses will include audible as well as visible output means in the immediate future.
The present invention seeks to mitigate these drawbacks by providing apparatus for processing smart cards and capable of allowing a user to determine, at least approximately, how much credit remains in a card.